Typically, an application sends message to send notifications of state changes or to broadcast information. Your component can broadcast messages to all the controls in a form, send messages to a particular control (or to the application itself), or even send messages to itself. 

There are several different ways to send a Windows message. Which method you use depends on why you are sending the message. The following topics describe the different ways to send Windows messages:

• Broadcasting a message to all controls in a form.
• Calling a control's message handler directly.
• Sending a message using the Windows message queue.
• Sending a message that does not execute immediately.